The present invention relates to a pixel, and in particular, to a pixel employed in an organic light emitting display panel.
FIG. 1 is a schematic diagram of a conventional pixel of a display array of an organic light emitting display panel. As shown in FIG. 1, a pixel 1 corresponds to interlaced data line DL and scan line SL and comprises a switch transistor 10, a storage capacitor 11, a driving transistor 12, and an organic light-emitting diode (OLED) 13. In FIG. 1, the driving transistor 12 is a PMOS transistor, for example.
Because the OLED 13 is a current-driving element, the brightness of the OLED 13 is determined by the intensity of the driving current Id provided by the driving transistor 12. The driving current Id is a drain current of the driving transistor 12 and refers to the driving capability thereof. The driving current Id is represented by the following equation:id=1/2·k·(vsg−|vth|)2 
where id, k, vsg and vth represent a value of the driving current Id, a conductive parameter of the driving transistor 12, a value of the source-gate voltage Vsg of the driving transistor 12, and a threshold voltage of the driving transistor 12 respectively.
Because the driving transistors in different regions of the display array are not electrically identical due to the fabrication process thereof, the threshold voltages of the driving transistors are unequal. When the pixels within different regions receive the same video signal, the driving current respectively provided by the driving transistors of the pixels is not equal due to the unequal threshold voltages of the driving transistors. Thus, brightness of the OLEDs is not equal, resulting in unequal OLED light-emission intensity in a frame cycle and uneven images displayed on the panel.